The present invention is directed, in general, to video encoding systems and, more specifically, to an encoding system for transmitting streaming video in a wireless network.
Real-time streaming of multimedia content in wireless networks has become an increasingly common application in recent years. A wide range of interactive and non-interactive multimedia applications, such as news-on-demand, live network television viewing, video conferencing, among others, rely on end-to-end streaming video or audio techniques. Unlike a downloaded video or audio file, which may be retrieved first in non-real time and viewed or played back later in real time, streaming video and audio applications require a transmitter that encodes and transmits a video or audio signal over a data network to a receiver, which must decode and display the video or audio signal in real time.
In a wireless network, it is important priority that video bit streams be delivered as reliably as possible. Layered source coding is one of the most effective schemes used to provide video transport systems with error resilience. In the layered source coding scheme, video data information is decomposed into a number of layers, each representing different perceptually relevant components of the video source. The base layer, which contains the most essential video information, can be used to generate a basic output video signal with an acceptable quality. A higher quality video signal can then be obtained by retrieving data from one or more enhancement layers that further improve the basic output video signal generated by the base layer encoder.
There are different ways for implementing layered source coding. For example, in systems with temporal domain layered coding, the base layer contains a bit stream with a low video frame rate and the enhancement layers contain incremental information for obtaining higher frame rates than possible with the original base layer. In systems with spatial domain layered coding, the base layer provides sub-sampled version codes for the original video sequence and the enhancement layers contain additional information for obtaining higher spatial resolution at the decoder.
In general, the different transport layers use different data streams with distinctly different tolerances for errors (known as channel errors) which are introduced during transport. To combat channel errors, the layered coding technique is usually combined with transport prioritization so that the base layer is delivered with a higher degree of error protection than the enhancement layers.
Transport prioritization has been implemented in a number of different ways in the prior art. One common transport prioritization method for wireless networks combines layered coding with different power levels so that each sub-stream transport layer is sent at a different transmit power level. The most important layer, the base layer is transmitted at highest power and the enhancement layers are transmitted at lower power, so that the overall power is kept within regulatory limits. The disadvantage to this method is that the finest levels of detail in the enhancement layers are transmitted at the lowest power.
In other conventional prioritization schemes, the base layer may be error checked and re-transmitted as often as necessary to ensure that it is properly received. Unfortunately, the re-transmission of the base layer occurs at the expense of transmission of the enhancement layer data.
There is therefore a need in the art for improved encoders and decoders for use in wireless networks capable of supporting real time data transmission to a mobile station, such as a video or audio receiver, a wireless computer, and the like. In particular, there is a need for improved encoders and decoders that are less susceptible to physical transport layer errors in streaming video and audio applications. More particularly, there is a need for encoders and decoders which deliver higher priority layered data using more reliable transmission modes and lower priority layered data using less reliable transmission modes.
To address the above-discussed deficiencies of the prior art, it is a primary object of the present invention to provide a wireless communication device capable of receiving an incoming RF data signal and deriving from the incoming RF data signal a base layer data stream and at least one enhancement layer data stream.
In an advantageous embodiment of the present invention, the wireless communication device comprises: 1) a base layer decoder, 2) at least one enhancement layer decoder, 3) a variable mode receiver capable of demodulating the RF incoming RF data signals in a plurality of physical modes, and 4) a receiver mode controller capable of controlling the plurality of physical modes of the variable mode receiver, wherein the receiver mode controller causes a first demodulated output signal of the variable mode receiver to be transferred to the base layer decoder when the variable mode receiver is operating in a first physical mode and causes a second demodulated output signal of the variable mode receiver to be transferred to the at least one enhancement layer decoder when the variable mode receiver is operating in a second physical mode.
According to one embodiment of the present invention, a bit error rate of the first physical mode is lower than a bit error rate of the second physical mode.
According to another embodiment of the present invention, the at least one enhancement layer decoder comprises a first enhancement layer decoder and a second enhancement layer decoder.
According to still another embodiment of the present invention, the receiver mode controller causes the second demodulated output signal of the variable mode receiver to be transferred to the first enhancement layer decoder when the variable mode receiver is operating in a second physical mode and causes a third demodulated output signal of the variable mode receiver to be transferred to the second enhancement layer decoder when the variable mode receiver is operating in a third physical mode.
According to yet another embodiment of the present invention, a bit error rate of the second physical mode is lower than a bit error rate of the third physical mode.
According to a further embodiment of the present invention, the plurality of physical modes comprise at least two of binary phase shift keying modulation, quadrature phase shift keying modulation, and quadrature amplitude modulation.
According to a still further embodiment of the present invention, the plurality of physical modes comprise a plurality of code rates.
According to a yet further embodiment of the present invention, the incoming RF data signal comprises a video signal.
According to another embodiment of the present invention, the incoming RF data signal comprises an audio signal.
It also is a primary object of the present invention to provide a wireless communication device capable of transmitting an outgoing RF data signal comprising a base layer data stream and at least one enhancement layer data stream. In an advantageous embodiment of the present invention, the wireless communication device comprises: 1) a base layer encoder, 2) at least one enhancement layer encoder, 3) a variable mode transmitter capable of modulating an input signal in a plurality of physical modes to thereby produce the outgoing RF data signal; and 4) a transmitter mode controller capable of controlling the plurality of physical modes of the variable mode transmitter, wherein the transmitter mode controller causes the variable mode transmitter to transmit a base layer output signal from the base layer encoder in a first physical mode and causes the variable mode transmitter to transmit at least one enhancement layer output signal from the at least one enhancement layer encoder in a second physical mode.
In one embodiment of the present invention, a bit error rate of the first physical mode is lower than a bit error rate of the second physical mode.
In another embodiment of the present invention, the at least one enhancement layer encoder comprises a first enhancement layer encoder and a second enhancement layer encoder.
In still another embodiment of the present invention, the transmitter mode controller causes the variable mode transmitter to transmit a first enhancement layer output signal from the first enhancement layer encoder in the second physical mode and causes the variable mode transmitter to transmit a second enhancement layer output signal from the second enhancement layer encoder in a third physical mode.
In yet another embodiment of the present invention, a bit error rate of the second physical mode is lower than a bit error rate of the third physical mode.
In a further embodiment of the present invention, the plurality of physical modes comprise at least two of binary phase shift keying modulation, quadrature phase shift keying modulation, and quadrature amplitude modulation.
In a still further embodiment of the present invention, the plurality of physical modes comprise a plurality of code rates.
In a yet further embodiment of the present invention, the incoming RF data signal comprises a video signal. According to another embodiment of the present invention, the incoming RF data signal comprises an audio signal.
The foregoing has outlined rather broadly the features and technical advantages of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features and advantages of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they may readily use the conception and the specific embodiment disclosed as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the invention in its broadest form.
Before undertaking the DETAILED DESCRIPTION, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document: the terms xe2x80x9cincludexe2x80x9d and xe2x80x9ccomprisexe2x80x9d and derivatives thereof mean inclusion without limitation; the term xe2x80x9corxe2x80x9d is inclusive, meaning and/or; the phrases xe2x80x9cassociated withxe2x80x9d and xe2x80x9cassociated therewithxe2x80x9d and derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like; and the term xe2x80x9ccontrollerxe2x80x9d means any device, system or part thereof that controls at least one operation, such a device may be implemented in hardware, firmware or software, or some combination of at least two of the same. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior, as well as future uses of such defined words and phrases.